[PATCH, i386]: Fix PR target/34312; spill failure with -O2 -fPIC -march=pentium-m on i386

[Uros Bizjak <ubizjak at gmail dot com>]

Hello!

The problem exposed by the testcase in PR target/34312 is, that due to 
implicit regparm function call register usage (%eax, %edx, %ecx) and 
-fpic usage of (%ebx), register allocator runs out of registers to 
allocate another QImode value.

There already exists the functionality, where implicit regparm value is 
lowered due to increased register pressure caused by global_regs usage. 
However, register pressure is also increased by fixed_regs in similar 
way (they are not available to register allocator), so it is somehow 
logical, that fixed_regs registers should be handled here in the same 
way as global regs.

Patch was bootstrapped on x86_64-pc-linux-gnu and regression tested on 
x86_64 with and without -m32. Patch is committed to SVN.

2007-12-05  Uros Bizjak  <ubizjak@gmail.com>

       PR target/34312
       * config/i386/i386.c (ix86_function_regparm): Also check for fixed
       registers when checking that regparm registers are available.
       Lower regparm value due to fixed registers usage in addition to
       global regs usage.

testsuite/ChangeLog:

2007-12-05  Uros Bizjak  <ubizjak@gmail.com>

       PR target/34312
       * gcc.target/i386/pr34312.c: New test.

Uros.

Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 130622)
+++ config/i386/i386.c	(working copy)
@@ -3198,9 +3198,9 @@ ix86_function_regparm (const_tree type, 
 	  struct function *f;
 
 	  /* Make sure no regparm register is taken by a
-	     global register variable.  */
+	     fixed register or global register variable.  */
 	  for (local_regparm = 0; local_regparm < 3; local_regparm++)
-	    if (global_regs[local_regparm])
+	    if (global_regs[local_regparm] || fixed_regs[local_regparm])
 	      break;
 
 	  /* We can't use regparm(3) for nested functions as these use
@@ -3222,11 +3222,12 @@ ix86_function_regparm (const_tree type, 
 					TYPE_ATTRIBUTES (TREE_TYPE (decl)))))
 	    local_regparm = 2;
 
-	  /* Each global register variable increases register preassure,
-	     so the more global reg vars there are, the smaller regparm
-	     optimization use, unless requested by the user explicitly.  */
+	  /* Each global register variable or fixed register usage
+	     increases register pressure, so less registers should be
+	     used for argument passing.  This functionality can be
+	     overriden by explicit regparm value.  */
 	  for (regno = 0; regno < 6; regno++)
-	    if (global_regs[regno])
+	    if (global_regs[regno] || fixed_regs[regno])
 	      globals++;
 	  local_regparm
 	    = globals < local_regparm ? local_regparm - globals : 0;
Index: testsuite/gcc.target/i386/pr34312.c
===================================================================
--- testsuite/gcc.target/i386/pr34312.c	(revision 0)
+++ testsuite/gcc.target/i386/pr34312.c	(revision 0)
@@ -0,0 +1,34 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target ilp32 } */
+/* { dg-require-effective-target fpic } */
+/* { dg-options "-O2 -march=pentium-m -fpic" } */
+
+typedef struct
+{
+  unsigned char seq[3];
+} JamoNormMap;
+
+static const JamoNormMap *
+JamoClusterSearch (JamoNormMap aKey, const JamoNormMap * aClusters,
+		   short aClustersSize)
+{
+  unsigned short l = 0, u = aClustersSize - 1;
+  unsigned short h = (l + u) / 2;
+
+  if ((aKey.seq[1] - aClusters[h].seq[1]) < 0)
+    return JamoClusterSearch (aKey, &(aClusters[l]), h - l);
+}
+
+short
+JamoSrchReplace (const JamoNormMap * aClusters, unsigned short aClustersSize,
+		 unsigned short * aIn, unsigned int * aLength,
+		 unsigned short aOffset)
+{
+  JamoNormMap key;
+
+  key.seq[0] = 0;
+  key.seq[1] = 1;
+  key.seq[2] = 2;
+
+  JamoClusterSearch (key, aClusters, aClustersSize);
+}